A bead portion that is a portion of a pneumatic tire that makes contact with a tire rim, needs to firmly fix the tire to the rim and so employs as a core a bead core formed by wrapping rubber cover tape on a metal wire formed in a ring shape.
In a configuration with the bead portion described above embedded into a carcass configuring a tire with the bead portion joined to the rim, such a bead core is the portion that transmits motive force of the drive wheels through the rim. The bead portion accordingly needs to have a certain degree of rigidity.
In order to secure rigidity, a flange shaped bead filler is mounted as reinforcement to the bead core, and a carcass is assembled with the bead filler in a mounted state.
In order to mount the bead filler to the bead core, generally a belt shaped member is wrapped around the periphery of the bead core. The bead filler is accordingly not an endless single unit flange, but instead has a join portion 17 at one location, as illustrated in FIG. 2.
The bead filler is designed to reinforce the bead portion of the tire, and so the ends of the member 14 need to accurately join at the join portion 17 without gaps or misalignment.
However, even though the belt shaped member 14 is accurately cut to a specific dimension, since it is made from soft uncured rubber, sometimes the ends of the member 14 do not accurately meet due to the tension force applied to the member 14 during winding, the winding speed and conditions of the operating environment such as the temperature or the humidity, and so there is sometimes misalignment at the join of the ends of the member 14.
FIG. 3 is a diagram illustrating situations of join defects of bead filler. The left hand side of FIG. 3 illustrates a state in which there is “step misalignment” in the top-bottom direction, namely in the width direction of the member between one end of the member 14 and the other end of the member 14 at the join portion of a belt shaped member. The center of FIG. 3 illustrates a state of an “opening” where a gap occurs between ends of the belt shaped member, and a band shaped member is not completely joined. The right hand side of FIG. 3 illustrates a state of a “gage difference” where one end of a belt shaped member rises up and is joined over the other end thereof.
Discovering join portion defects such as those illustrated in FIG. 3 is performed using visual inspection by inspectors, and good/no-good determination of join portions depends on the experience and number of inspectors.
However, due to determination by visual inspection by an inspector involving the subjectivity of the inspector, the existence of different determination standards cannot be discounted, with there being concern regarding variation in good/no-good determination of the join portions depending on the different inspectors. Moreover, the occurrence of determination mistakes cannot be discounted even for a veteran inspector.
Considerable man-hours are also involved in checking, and since all of these man-hours are related to visual confirmation, there is also an issue regarding the large amount of time required for inspection.
Thus a bead inspection device is described in JP-A No. 2007-76289 wherein the entire periphery of a stiffener applied bead (a bead application bead filler) is captured as an inspection target by successive images, and then based on the captured images, a length L1 between a lower end at one side portion of a stiffener (bead filler) joined to the outer peripheral face of a bead and the end at the one side, and a length L2 between a lower end at the other side portion of the stiffener joined to the outer peripheral face of the bead and the end at the other side of the bead, are computed, and determination is made as to whether or not L1 and L2 fall within a permitted range.
Moreover, in JP-A No. 2008-74329 a bead filler inspection device is described that employs a two-dimensional displacement sensor, wherein a laser is illuminated in a line form onto a bead application bead filler, shape deformation of the bead application bead filler is measured from reflected light in the thickness direction (the Z axis direction) of the bead application bead filler, each position of the bead application bead filler is measured in the width direction (the X axis direction), and from these measurement results, two dimensional shape data (a profile) of a cross-section in the Z axis direction is generated for the bead application bead filler. Determination is then made as to whether or not the dimensions of the generated shape data match specific reference values in each of the thickness (Z axis direction) and the width (X axis direction).